Generally, data receivers for use in utility automatic meter reading have been proposed. Various methods have been employed to insure accuracy and compatability with both the communications medium employed and transponders furnishing the data. While data gathering systems approaching accuracies of 100 percent are in common use today, such systems are very expensive to manufacture and maintain. Some systems such as gas, water and electric utility meter reading systems need not be capable of these accuracies. The relatively low cost of the product does not justify the cost of extreme accuracies in either measurement or data gathering. In addition, the magnitude of the number of "points of sale" -- in the hundreds of millions -- requires consideration of the cost of transponder and encoder devices installed at each meter.
A practical utility meter reading system, therefore, compromises accuracy to an acceptable level in order to meet the economic needs of the system.
Having compromised accuracy at the point of data delivery then, by using the least expensive technique available, it is desirable to define inaccuracies as completely as possible so that they may be recognized and appropriate measures taken to correct the data at the data collection center where expense will be minimal.
Certain other deficiencies are apparent in previous designs. Where the system is to be used to receive data over a switched telephone network, it is highly desirable for the data receiver to include signalling means to activate a transponder to which it may be connected at a given instant. Additionally, it is desirable in both the technological and economic sense that it differentiate between single and multiple party lines. The ability to control the connection to the subscriber telephone line during the data transmission interval is also necessary in order to insure minimal interference with a subscriber's use of his telephone.
The present invention is directed towards various improvements in a data receiver which is capable of operation in a single receiving mode and a plurality of transmitting modes and which has the ability to release the telephone line to the subscriber should he so request. It is also directed toward a data receiver which has the ability to detect certain invalid data and correct it in order to enhance overall accuracy.